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I'm a beginner in this field and I have to buy this clip from shutter-stock.

This clip comes with some pre-rendered patterns and has an alpha-matte version.

My question is : I want to use different pattern for the ripped paper, how can I achieve that ? and can the alpha-matte version used for this purpose ? if no .. it used for what ??

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1 Answer 1

Changing the pattern of the paper will be too difficult, because you would have to map the pattern around the roll, too. But you can change the color with some Hue/Saturation/Value effect.

So, what are the black/white alpha-matte sections for? The author had to append them at the end, because in the process chain at Shutterstock the video could be transcoded and the alpha channel could get lost. In your own video editor you will have to cut these black/white sections out and re-apply them as alpha clip over your color clip. How to do this can be different in After Effects, Final Cut Pro, ...

But now the most interesting part. Why did the author append two alpha-matte versions, which seem to be equal?

Only after calculating the difference between the two versions I saw it. In this picture gray means that the pixels of the two images are equal, and black or white means that there is some difference.

difference of the two alpha-matte clips

This means that the first alpha-matte is for the paper including the white ripped edge, where-as the second one is for the paper surface without the ripped edge. If you want to color the paper, apply the effect just together with the second alpha-matte, and the edge will stay white.

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Thanks a lot for your valuable information, but do you mean that it's too difficult to change the original clip.. I have been told that in order to do any changes you have to have the source file as an AE project file or 3DsMax project file and so you can edit and change what ever you want, but now you can't because it's a rendered clip. Am I right? –  Saeed Jan 28 '13 at 18:29
    
Yes, this is right. Without the project file it's too complicated. Of course, if you have a lot of time, you could export the video into a sequence of images and then manipulate the 100+ images in Photoshop. But in my opinion this would only be an option if the client really wants this and pays for this extra work. For example, if he really wants his logo on the paper surface. But just for having another pattern it's not worth the effort. –  Fred42vid Jan 29 '13 at 7:41

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